Poor service from MTN

I called MTN on the 21 August to block my phone, the consultation said they can’t blacklist a phone with a passport number I should ask a friend that has a South African ID. I asked my friend then they blocked my phone with his ID. I submitted the claim to the insurance and the insurance said they want as official letter from MTN stating that they asked me to block my phone with my friend’s ID. I called MTN and they said to me I should go to an MtN store for the letter. I went to 3 different stores and they refused to give me the letter saying that call centre is the one that is supposed to give me the letter. I went back and forth without getting the letter. Call centre only sent me the sms which the insurance declined saying they want the letter. Now my claim has been rejected because MTN refused to give me the letter 😭😭💔💔.